JP2010113099A - Display device and display control method - Google Patents

Abstract

An effect of reducing power consumption can be obtained more reliably, and a high-quality display device and a control method thereof are realized.
A liquid crystal display device 100 displays at least one selected pixel block 1A on each pixel constituting the pixel block 1A obtained from display data of an image to be displayed in a display area of the liquid crystal display panel 1. The gray level luminance extraction unit 51 that calculates the gray level luminance of the image to be displayed, and the number of pixels that the image of the specific gray level luminance calculated by the gray level luminance extraction unit 51 is displayed for each gray level luminance. And a luminance adjustment unit 53 that adjusts the luminance of light emitted from the subunit 3A corresponding to the selected pixel block 1A according to the result of the accumulation by the histogram generation unit 52. .
[Selection] Figure 1

Description

  The present invention relates to a display device including a liquid crystal display panel as a display unit, and a backlight unit provided to correspond to the liquid crystal display panel, and a control method thereof.

  In general, a liquid crystal display panel as a display unit of a liquid crystal display device has a configuration in which a transparent substrate opposed to a liquid crystal is used as an envelope, and a large number of pixels are formed in the liquid crystal spreading direction. Each pixel is provided with a pair of electrodes for generating an electric field. In the liquid crystal display panel, the light transmittance of the liquid crystal is controlled according to the electric field generated from each electrode.

  On the other hand, on the back surface of the liquid crystal display panel, there is provided a backlight unit serving as a light source for irradiating each liquid crystal whose light transmittance is controlled, that is, for lighting the liquid crystal display panel. It is done. Conventionally, various backlight units are known. In particular, in recent years, backlight units in which light emitting diodes (LEDs) are arranged have become mainstream.

  Conventionally, in the backlight unit, the power consumption has been increased by always lighting the liquid crystal display panel with a high luminance during display on the liquid crystal display device, and thus further reduction in power consumption has been demanded.

  As a technology for reducing the power consumption of the backlight unit, the backlight unit is divided into a plurality of subunits each capable of adjusting the brightness independently, and each subunit is input to the pixel block of the corresponding liquid crystal display panel. Various techniques for dynamically adjusting the brightness in accordance with the video signal are proposed. For example, Patent Document 1 discloses the technique.

  The liquid crystal display device disclosed in Patent Document 1 includes means for calculating the maximum luminance from a video signal input to a pixel block of the liquid crystal display panel, and a subunit corresponding to the pixel block corresponding to the size thereof. Is adjusting the brightness of the light emitted by.

  Specifically, in the liquid crystal display device disclosed in Patent Document 1, as a first technique for reducing power consumption, display data input to each pixel in each pixel block is used for each pixel. Among the supplied video signals, the highest luminance is calculated, and the luminance of the opposing subunits is adjusted in accordance with the maximum luminance in each pixel block.

Further, in the liquid crystal display device disclosed in Patent Document 1, as a second technique for reducing the power consumption, the display data input to each pixel in each pixel block is supplied to each pixel. Among the video signals, the highest luminance is calculated, and the luminance value of the display data input to each pixel of the pixel block is increased in correspondence with the magnitude of the highest luminance in each pixel block. The luminance of the subunit facing the pixel block is reduced corresponding to the maximum luminance.
JP 2004-191490 A (published July 8, 2004)

  However, in the liquid crystal display device disclosed in Patent Document 1, in both the first technique and the second technique, only the information relating to the maximum luminance of the image displayed on the pixel block is used. In contrast, the brightness of light emitted from the corresponding subunit is adjusted.

  For this reason, in the image displayed in the pixel block, for example, even if there is only one white point in the entire black screen, the subunit corresponding to the pixel block lights the pixel block with high brightness. Will be allowed to.

  In the above case, not only the effect of reducing the power consumption by reducing the brightness of the light emitted from the backlight unit, but also black floating caused by lighting a black screen with high brightness occurs. As a result, there is a problem that the image quality may be significantly impaired.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a high-quality display device and a control method thereof that can more reliably obtain the effect of low power consumption. It is to provide.

  In order to solve the above problem, a display device according to the present invention includes a liquid crystal display panel whose display area is divided into a plurality of pixel blocks, and a plurality of sub-pixels for irradiating light for each of the plurality of pixel blocks. A backlight unit divided into units, and each subunit is a display device capable of independently adjusting the brightness of light applied to each corresponding pixel block, and at least selected Gray level luminance calculation for calculating the gray level luminance of the image displayed on each pixel constituting the pixel block, obtained from data of the image to be displayed in the display area of the liquid crystal display panel, for one pixel block. A pixel integrating unit that integrates the number of pixels for which the gray level luminance is calculated for each gray level luminance calculated by the gray level luminance calculating unit, Depending on the result of element integration unit is integrated, is characterized in that each sub-unit corresponding to the selected said pixel block and a brightness adjusting portion that adjusts the brightness of light to be irradiated.

  In addition, in order to solve the above-described problem, the display control method according to the present invention has a liquid crystal display panel whose display area is divided into a plurality of pixel blocks, and for irradiating light to each of the plurality of pixel blocks. A backlight unit divided into a plurality of subunits, and each subunit is a display control method capable of independently adjusting the luminance of light applied to each corresponding pixel block, With respect to at least one selected pixel block, the gray level luminance of the image displayed on each pixel constituting the pixel block, obtained from the data of the image to be displayed in the display area of the liquid crystal display panel, is calculated. For each gray level luminance calculated by the gray level luminance calculation step and the gray level luminance calculation step, the pixel for which the gray level luminance is calculated And a luminance adjustment step of adjusting the luminance of light emitted from each subunit corresponding to the selected pixel block according to the result of the integration of the pixel integration step. It is a feature.

  According to the above configuration, the gray level luminance of the image displayed on each pixel constituting the pixel block is calculated, and from the subunit corresponding to the pixel block according to the integration result of the number of pixels for each luminance. The brightness of the irradiated light can be adjusted.

  In other words, in the display device and the control method thereof according to the present invention, the gray level luminance distribution of the image displayed in the pixel block, that is, each gray level luminance and the number of pixels for which each gray level luminance is calculated, The luminance of light emitted from the corresponding subunit is adjusted for the pixel block using the information on the relationship of.

  Here, in the image displayed in the pixel block, for example, when there is only one white point on the whole black screen, each gray level luminance and each gray level luminance of the image displayed in the pixel block are displayed. The relationship between the calculated number of pixels and the number of pixels is almost the same as the relationship when the entire screen is a black screen. Therefore, the subunit corresponding to the pixel block can light the pixel block with low luminance in almost the same manner as in the case where the whole is a black screen in the display device according to the related art.

  In the above case, the effect of reducing power consumption by reducing the brightness of the light emitted from the backlight unit is more reliably exhibited than before, and the black screen is lit with high brightness. It is possible to suppress the occurrence of black floating and the accompanying deterioration in image quality.

  Therefore, in the display device and the control method thereof according to the present invention, the effect of reducing power consumption can be more reliably obtained, and a high-quality display device and the control method thereof can be realized.

  Further, in the display device according to the present invention, the brightness adjustment unit may adjust the brightness adjustment value of light emitted from each of the subunits between the brightness indicating white display and the brightness indicating black display. It is characterized by allocating according to the result of integration by the integration unit.

  When the entire pixel block is in white display, it is the brightest of all the display patterns. Therefore, the luminance indicating this white display is set as the highest luminance among the adjustment values of the luminance of light emitted by the subunit. . On the other hand, when the entire pixel block is in black display, it is the darkest of all display patterns. Therefore, the luminance indicating this black display is set as the lowest luminance among the adjustment values of the luminance of light emitted by the subunit. Set. As a result, it is possible to easily estimate and adjust the maximum and minimum luminances, and to suppress the occurrence of inversion of light and dark in an image including white display and / or black display. Video can be realized.

  Further, as a specific example of how the luminance adjustment unit determines the adjustment value of the luminance of light emitted from the subunit, the display device according to the present invention is configured such that the luminance adjustment unit is calculated by the gray level luminance calculation unit. For each gray level luminance, a first is obtained to obtain the product of the unit adjustment value of the luminance of light to be given to one pixel for which the gray level luminance is calculated and the number of pixels for which the gray level luminance is calculated. And a second calculation that adds all the products obtained by the first calculation together to determine an adjustment value of the luminance of light emitted by each of the subunits. It is a feature.

  According to the above configuration, the brightness adjustment value of the light emitted from the subunit adjusted by the brightness adjustment unit is the gray level brightness and the gray level brightness of the image displayed in the corresponding pixel block. This can be determined as appropriate by performing the first and second calculations using information on the relationship between the calculated number of pixels.

  When determining the adjustment value of the luminance of light emitted from the subunit by the first and second calculations, each of the unit adjustment values increases monotonously, more preferably in proportion to the increase in the gray level luminance. It is preferable to be determined so that

  According to the above configuration, each unit adjustment value is a function that increases monotonously, more preferably in proportion to the increase in gray level luminance. Accordingly, in correspondence with the brightness and darkness of the image displayed in the pixel block, the pixel block is brightened in the pixel block portion where the image is bright, and the pixel block is lit dark in the pixel block portion where the image is dark. Can be applied more clearly.

  Further, in the display device according to the present invention, in the second calculation, the products obtained by the first calculation are added in order from the smallest gray level luminance, and the one product is added. When the addition operation value obtained in this way becomes larger than a predetermined maximum value corresponding to the addition operation value, the addition operation value is replaced with the corresponding maximum value.

  According to the above configuration, the product of the unit adjustment value and the number of pixels for which the gray level luminance corresponding to the unit adjustment value is calculated is obtained by adding them in order from the smallest gray level luminance. When the addition operation value becomes larger than a predetermined maximum value corresponding to the addition operation value, the addition operation value is replaced with the corresponding maximum value. If the addition calculation value becomes too large, the adjustment value of the luminance of the light emitted by the subunit, which is obtained when the second calculation is completed, becomes a very large value, which increases the power consumption. However, if the maximum value that can be taken by the addition calculation value is set in advance in each addition calculation value, the adjustment value becomes very large, and accordingly, consumption It can suppress that electric power becomes high.

  It should be noted that it is preferable that each of the corresponding maximum values is determined so as to increase monotonously, more preferably in proportion to the increase of the gray level luminance related to each of the addition calculation values.

  According to the above configuration, each of the maximum values is a function that increases monotonously and more preferably is proportional to the increase in gray level luminance. Accordingly, in correspondence with the brightness and darkness of the image displayed in the pixel block, the pixel block is brightened in the pixel block portion where the image is bright, and the pixel block is lit dark in the pixel block portion where the image is dark. Can be applied more clearly.

  Further, in the display device according to the present invention, the gray level luminance calculation unit, the pixel integration unit, and the luminance adjustment unit may be configured for a plurality of the pixel blocks and the subunits corresponding to the pixel blocks. In accordance with the luminance of light emitted from the subunit corresponding to at least one of the selected pixel blocks, the luminance of light emitted from other subunits adjacent to the subunit, which performs each of the above processes. Is adjusted twice or more.

  A certain pixel block is further irradiated with light from a subunit corresponding to a pixel block adjacent thereto by diffusion. Here, for example, when the adjustment value of the light emitted from the subunit corresponding to the pixel block close to a certain pixel block is large (that is, the subunit is brightly shining), from the subunit Since the irradiated light is further irradiated to the certain pixel block, even if the adjustment value of the light irradiated to the subunit corresponding to the certain pixel block is reduced, the desired certain pixel The brightness of the block can be obtained. As described above, the pixel block value is calculated again according to the value of the adjacent pixel block, and a new adjustment value of the light emitted from the corresponding subunit is obtained, thereby further reducing the power consumption. .

  In the display device according to the present invention, it is preferable that the backlight unit includes a light emitting diode as a light source for irradiating light.

  As described above, in the display device according to the present invention, the display area is divided into a liquid crystal display panel divided into a plurality of pixel blocks and a plurality of subunits for irradiating light for each of the plurality of pixel blocks. A backlight unit, and each subunit is a display device capable of independently adjusting the luminance of light applied to each corresponding pixel block, wherein at least one selected pixel block The gray level luminance calculation unit for calculating the gray level luminance of the image displayed on each pixel constituting the pixel block, obtained from the data of the image to be displayed in the display area of the liquid crystal display panel, and the gray level For each gray level luminance calculated by the level luminance calculation unit, the pixel integration unit that integrates the number of pixels for which the gray level luminance is calculated and the pixel integration unit Depending on the result, and a brightness adjusting portion that adjusts the brightness of light each subunit is irradiated corresponding to the pixel block is selected.

  The display control method according to the present invention includes a liquid crystal display panel having a display area divided into a plurality of pixel blocks, and a back divided into a plurality of subunits for irradiating light for each of the plurality of pixel blocks. A light unit, and each subunit is a display control method capable of independently adjusting the luminance of light applied to each corresponding pixel block, wherein at least one selected pixel block A gray level luminance calculating step for calculating a gray level luminance of the image displayed on each pixel constituting the pixel block, obtained from data of an image to be displayed in the display area of the liquid crystal display panel; Pixel integration step for integrating the number of pixels for which the gray level luminance is calculated for each gray level luminance calculated in the level luminance calculation step , According to a result of the pixel integration step is integrated, having a luminance adjusting step of adjusting the brightness of light each subunit is irradiated corresponding to the pixel block is selected.

  Therefore, the effect of reducing the power consumption can be obtained more reliably and the image quality can be improved.

  The best mode for carrying out the present invention will be described below with reference to FIGS.

  FIG. 1 is a diagram showing a schematic configuration of a display device according to an embodiment of the present invention.

  A liquid crystal display device (display device) 100 shown in FIG. 1 includes a liquid crystal display panel 1, a diffusion plate 2 as diffusion means, and a backlight unit 3.

  The liquid crystal display panel 1, the diffusion plate 2, and the backlight unit 3 are arranged on the liquid crystal display device 100 in this order from the viewer side of the liquid crystal display device 100 so as to face each other.

  The liquid crystal display panel 1 uses a transparent substrate (not shown) or the like arranged opposite to the liquid crystal as an envelope, and spreads the liquid crystal, that is, a direction substantially perpendicular to the surface of the liquid crystal display panel 1 here. In this configuration, a large number of pixels are formed. Each pixel is provided with a pair of electrodes for generating an electric field. In the liquid crystal display panel 1, the light transmittance of the liquid crystal corresponding to each electrode is controlled according to the electric field generated from each electrode. Further, when the liquid crystal display panel 1 is irradiated with light from the backlight unit 3, the light passes through the liquid crystal display panel 1 and reaches the eyes of the viewer of the liquid crystal display device 100. .

  Further, the liquid crystal display device 100 includes a liquid crystal driving circuit 6 including a scanning signal driving circuit and a video signal driving circuit (not shown) around the liquid crystal display panel 1 serving as a display area.

  Display data (image data to be displayed in the display area) input from the outside of the liquid crystal display device 100 is input to the liquid crystal driving circuit 6. When display data (for example, a video signal) is input, the liquid crystal driving circuit 6 generates a scanning signal and a video signal corresponding to the display data and supplies them to the liquid crystal display panel 1. The liquid crystal display panel 1 displays an image corresponding to the video signal by applying the video signal to the scanning lines sequentially selected by the scanning signal supplied from the liquid crystal driving circuit 6.

  The liquid crystal display panel 1 is capable of color display, and each of the three pixels provided adjacent to each other has red (Red), green (Green), and blue (Blue) colors. Built-in filter.

  The backlight unit 3 is formed on a substrate having approximately the same size as the liquid crystal display panel 1. The substrate is disposed so that each surface of the substrate faces the liquid crystal display panel 1, and a large number of light emitting diodes 4 are arranged in a matrix on the surface of the substrate on the liquid crystal display panel 1 side. Yes.

  Each of the plurality of light emitting diodes 4 does not have to be arranged corresponding to each pixel of the liquid crystal display panel 1. For example, one light emitting diode 4 is provided for a plurality of adjacent pixels of the liquid crystal display panel 1. May be provided so as to face each other.

  The diffusing plate 2 is made of, for example, an optical sheet, and diffuses light of each color irradiated from the backlight unit 3 and passes it to the liquid crystal display panel 1 side.

  The backlight unit 3 includes a plurality of light emitting diodes 4.

  As shown in FIG. 1, the backlight unit 3 is divided into a plurality of subunits 3 </ b> A in units of subunits 3 </ b> A that are composed of light emitting diodes 4 adjacent to each other. That is, the backlight unit 3 is divided into a plurality of subunits 3 </ b> A for irradiating the liquid crystal display panel 1 with light emitted from the light emitting diodes 4. In each subunit 3A, the luminance of light emitted from the corresponding light emitting diode 4 can be independently adjusted for each subunit 3A.

  For example, in the case of the present embodiment, the backlight unit 3 is divided into a plurality of parts in both the x direction and the y direction that are parallel to the substrate surface of the backlight unit 3 and perpendicular to each other. And may be divided into a plurality of parts in only one of the y directions. Further, the number of divisions of the backlight unit 3 may be arbitrary, but needless to say, it is preferable to increase the number of divisions.

  Furthermore, the liquid crystal display panel 1 is divided into a plurality of pixel blocks 1A corresponding to the plurality of subunits 3A. Light from the subunit 3A is irradiated to the pixel block 1A corresponding to the subunit 3A through the diffusion plate 2.

  Here, as a point to be noted, the liquid crystal display device 100 includes the display gradation analysis device 5. The display gradation analysis device 5 includes a gray level luminance extraction unit (gray level luminance calculation unit) 51, a histogram creation unit (pixel integration unit) 52, and a luminance adjustment unit 53.

  From here, each processing step implemented by the display gradation analyzer 5 having the above-described configuration will be described.

  Hereinafter, for the sake of convenience, a system composed of a certain pixel block 1A and a single subunit 3A corresponding thereto (that is, irradiating light to the certain pixel block 1A facing each other). Is referred to as a “unit display system”.

  In this embodiment, as an example of the display gradation analysis apparatus 5, each processing step of the display gradation analysis apparatus 5 for one unit display system will be described. However, the display gradation analysis apparatus 5 may perform the following processing steps for each of a plurality of unit display systems. The display gradation analysis device 5 most preferably performs the following processing steps for every unit display system existing in the liquid crystal display device 100.

  The display data input to the liquid crystal driving circuit 6 and input from the outside of the liquid crystal display device 100 is further input to the gray level luminance extraction unit 51 of the display gradation analysis device 5.

  The gray level luminance extraction unit 51 displays, from the input display data, the pixel block 1A constituting the unit display system, which is displayed on the pixels constituting the pixel block 1A, obtained from the display data. Gray level luminance (hereinafter referred to as “pixel gray level luminance”) is calculated for each of a plurality of pixels (gray level luminance calculating step).

  Note that the gray level luminance extraction unit 51 calculates the gray level luminance of the pixel to be calculated, for example, in the following manner (A) to (C).

    (A) A maximum value among RGB (Red-Green-Blue) values of an image to be displayed on a pixel is set as the gray level luminance of the pixel.

    (B) An average value of RGB values of an image to be displayed on a pixel is set as the gray level luminance of the pixel.

    (C) The Y value of YCbCr of the image to be displayed on the pixel is set as the gray level luminance of the pixel.

  The Y value of YCbCr can be derived from the following mathematical formula (1) based on the RGB values.

Y = 0.29891 × R + 0.58661 × G + 1.448 × B (1)
The histogram creating unit 52 accumulates the number of pixels calculated by the gray level luminance extracting unit 51 and displaying an image of a specific gray level luminance for each gray level luminance, and creates a histogram indicating the accumulation result. (Pixel integration step).

  FIG. 2 is a histogram showing an example of histogram creation in the histogram creation unit 52.

  The histogram created by the histogram creating unit 52 is, for example, as shown in FIG. 2, in which the horizontal axis represents the gray level luminance of the pixel, the vertical axis represents the number of pixels, and the gray level luminance in the pixel block 1A constituting the unit display system. What is necessary is just to show the relationship between each gray level brightness | luminance which the extraction part 51 calculated, and the pixel number from which each gray level brightness | luminance was calculated.

  According to the histogram shown in FIG. 2, in the pixel block 1A configuring the unit display system, the number of pixels for which the gray level luminance I1 is calculated by the gray level luminance extraction unit 51 is N1. Similarly, the number of pixels for which the gray level luminance I2 is calculated is N2, the number of pixels for which the gray level luminance I3 is calculated is N3, the number of pixels for which the gray level luminance I4 is calculated is N4, and the gray level luminance I5 is The calculated number of pixels is N5.

  However, the process of “creating a histogram” in the histogram creating unit 52 is not an essential process. Even if the histogram creation unit 52 does not create a histogram as shown in FIG. 2, the relationship between each gray level luminance calculated by the gray level luminance extraction unit 51 and the number of pixels from which each gray level luminance is calculated, That is, it is sufficient to know the number of pixels calculated for each gray level luminance.

  The luminance adjustment unit 53 adjusts the luminance of light emitted from the subunit 3A constituting the unit display system according to the histogram (see FIG. 2) created by the histogram creation unit 52 (luminance adjustment step).

  From here, the point which the brightness | luminance adjustment part 53 performs the calculation for adjusting the brightness | luminance of the light which the subunit 3A which comprises a unit display system irradiates according to the said histogram is demonstrated in detail.

  The luminance adjustment unit 53 performs the following calculation on the gray level luminances I1 to Ix (where x is a natural number) indicating all types of gray level luminances calculated by the gray level luminance extraction unit 51. However, the gray level luminance I1 has the smallest luminance among the calculated gray level luminances, and the gray level luminance Ix has the largest luminance among the calculated gray level luminances. is there. Furthermore, each gray level luminance I1 to Ix has already shown an example in the case of x = 5 in the histogram of FIG. 2, and becomes I1,..., Ix in ascending order of the gray level luminance. Shall.

  First, regarding the selected gray level luminance Iy (where y is a natural number and 1 ≦ y ≦ x), the luminance of light to be given to one pixel for which the gray level luminance Iy is calculated A product Sy of the adjustment value (unit adjustment value) F (Iy) and the number of pixels Ny from which the gray level luminance Iy has been calculated is obtained (first calculation).

  Subsequently, an addition operation value K (y−1), which will be described later, and a maximum value M (y−1), which will be described later, which are selected in advance as the above-described calculation result regarding the product Sy and the gray level luminance I (y−1). One of them is added to obtain an addition operation value Ky (second operation). However, when y = 1, the addition operation value Ky (ie, the addition operation value K1) is equal to the product Sy (ie, the product S1). Further, when the pixel number Ny from which the gray level luminance Iy is calculated is 0, the addition calculation value Ky is equal to the addition calculation value K (y−1).

  Subsequently, the addition operation value Ky is compared with a predetermined maximum value My corresponding to the addition operation value Ky. At this time, when the addition calculation value Ky is larger than the maximum value My, the addition calculation value Ky is replaced with the maximum value My to obtain a calculation result (adjustment value) by the luminance adjustment unit 53 regarding the gray level luminance Iy.

  Then, by performing the above calculation for all of the gray level luminances I1 to Ix, the luminance adjustment unit 53 determines the luminance of the light irradiated by the subunit 3A constituting the unit display system.

  Below, based on the histogram shown in FIG. 2, the point which performs this calculation is demonstrated more concretely with reference to FIG.

  First, in the histogram shown in FIG. 2, with respect to the smallest gray level luminance I1, the light luminance adjustment value (unit adjustment value) F (I1) to be given to one pixel for which the gray level luminance I1 is calculated is The product S1 of the pixel number N1 for which the gray level luminance I1 is calculated is obtained (first calculation).

  Subsequently, the product S1 is compared with a predetermined maximum value M1 corresponding to the product S1. When the product S1 is larger than the maximum value M1, the product S1 is replaced with the maximum value M1 to obtain a calculation result (adjustment value) by the luminance adjustment unit 53 regarding the gray level luminance I1, but according to the graph shown in FIG. Since the product S1 is smaller than the maximum value M1, the calculation result by the luminance adjustment unit 53 regarding the gray level luminance I1 is the product S1.

  Subsequently, in the histogram shown in FIG. 2, with respect to the gray level luminance I2 that is the second smallest after the gray level luminance I1, the light luminance adjustment value (unit adjustment) to be given to one pixel for which the gray level luminance I2 is calculated. A product S2 of the value) F (I2) and the number N2 of pixels for which the gray level luminance I2 is calculated is obtained (first calculation). Subsequently, the product S2 and the product S1 selected as the calculation result regarding the gray level luminance I1 are added to obtain an addition calculation value K2 (second calculation).

  Subsequently, the addition calculation value K2 is compared with a predetermined maximum value M2 corresponding to the addition calculation value K2. When the addition calculation value K2 is larger than the maximum value M2, the addition calculation value K2 is replaced with the maximum value M2, and the calculation result (adjustment value) by the luminance adjusting unit 53 regarding the gray level luminance I2 is shown in FIG. According to the graph, since the addition calculation value K2 is smaller than the maximum value M2, the calculation result by the luminance adjustment unit 53 regarding the gray level luminance I2 is set as the addition calculation value K2.

  Subsequently, in the histogram shown in FIG. 2, with respect to the gray level luminance I3 which is the second smallest after the gray level luminance I2, an adjustment value (unit adjustment) of light luminance to be given to one pixel for which the gray level luminance I3 is calculated. A product S3 of the value) F (I3) and the number of pixels N3 from which the gray level luminance I3 is calculated is obtained (first calculation). Subsequently, the product S3 and the addition calculation value K2 selected as the calculation result regarding the gray level luminance I2 are added to obtain an addition calculation value K3 (second calculation).

  Subsequently, the addition calculation value K3 is compared with a predetermined maximum value M3 corresponding to the addition calculation value K3. When the addition calculation value K3 is larger than the maximum value M3, the addition calculation value K3 is replaced with the maximum value M3 to obtain the calculation result (adjustment value) by the luminance adjustment unit 53 regarding the gray level luminance I3. According to the graph, since the addition calculation value K3 is smaller than the maximum value M3, the calculation result by the luminance adjustment unit 53 regarding the gray level luminance I3 is the addition calculation value K3.

  Subsequently, in the histogram shown in FIG. 2, with respect to the gray level luminance I4 that is the second smallest after the gray level luminance I3, the light luminance adjustment value (unit adjustment) to be given to one pixel for which the gray level luminance I4 is calculated. (Value) F (I4) and the product S4 of the number of pixels N4 from which the gray level luminance I4 is calculated are obtained (first calculation). Subsequently, the product S4 and the addition calculation value K3 selected as the calculation result regarding the gray level luminance I3 are added to obtain an addition calculation value K4 (second calculation).

  Subsequently, the addition operation value K4 is compared with a predetermined maximum value M4 corresponding to the addition operation value K4.

  Here, according to the graph shown in FIG. 3, the addition operation value K4 is larger than the maximum value M4. For this reason, the calculation result by the luminance adjustment unit 53 regarding the gray level luminance I4 is replaced from the addition calculation value K4 to the maximum value M4. Therefore, the calculation result by the luminance adjustment unit 53 regarding the gray level luminance I4 is the maximum value M4.

  Subsequently, in the histogram shown in FIG. 2, with respect to the largest gray level luminance I5, the light luminance adjustment value (unit adjustment value) F (I5) to be given to one pixel for which the gray level luminance I5 is calculated. ) And the number N5 of pixels for which the gray level luminance I5 has been calculated, a product S5 is obtained (first calculation). Subsequently, the product S5 and the maximum value M4 selected as the calculation result relating to the gray level luminance I4 are added to obtain an addition calculation value K5 (second calculation).

  Subsequently, the addition operation value K5 is compared with a predetermined maximum value M5 corresponding to the addition operation value K5. When the addition calculation value K5 is larger than the maximum value M5, the addition calculation value K5 is replaced with the maximum value M5 to obtain the calculation result (adjustment value) by the luminance adjustment unit 53 regarding the gray level luminance I5. According to the graph, since the addition calculation value K5 is smaller than the maximum value M5, the calculation result by the luminance adjustment unit 53 regarding the gray level luminance I5 is the addition calculation value K5.

  In this manner, the light emitted from the subunit 3A constituting the unit display system to the pixel block 1A constituting the unit display system, which is calculated by the above processing steps in the display gradation analyzing device 5, is displayed. The brightness adjustment value is input to the backlight drive circuit 7. The backlight drive circuit 7 determines the luminance of each light emitting diode 4 included in the subunit 3A according to the adjustment value, and causes each light emitting diode 4 to emit light.

  The backlight drive circuit 7 controls each light emitting diode 4 by pulse width modulation. Specifically, while the current flowing through the light emitting diode 4 is constant regardless of the change in the adjustment value, the length of the light emission period (high level pulse) corresponding to each adjustment value (high level pulse and low level) is low. The luminance when each light emitting diode 4 is caused to emit light is controlled by appropriately changing the duty ratio with the level pulse. Note that the length of the high-level pulse monotonously increases with respect to the adjustment value. Thereby, since the most efficient current condition in each light emitting diode 4 is always used, the light emission efficiency is improved, and as a result, the power consumption can be reduced. Further, the luminance of the light emitting diode 4 is easily adjusted because the relationship with the duty ratio is proportional. The driving principle of each light emitting diode 4 by the backlight driving circuit 7 is generally implemented conventionally.

  According to the above configuration, the gray level luminance of the image displayed on each pixel constituting the pixel block 1A constituting the unit display system is calculated from the display data, and according to the integration result, the unit display system is calculated. It is possible to adjust the luminance of light emitted from the subunit 3A constituting the.

  In other words, in the liquid crystal display device 100, the gray level luminance distribution of the image displayed in the pixel block 1A, that is, the gray level luminances I1 to Ix and the number of pixels for which the gray level luminances I1 to Ix are calculated. Using the information regarding the relationship between N1 to Nx, the luminance of light emitted from the corresponding subunit 3A is adjusted.

  Here, in the image displayed in the pixel block 1A, for example, when there is only one white point in the entire black screen, the gray level luminances I1 to Ix of the image displayed in the pixel block 1A are The relationship between the number of pixels N1 to Nx is almost the same as the relationship when the entire screen is a black screen. Accordingly, the subunit 3A corresponding to the pixel block 1A can light the pixel block 1A with low luminance in almost the same manner as in the case of the display device according to the related art, which is a black screen as a whole.

  In the above case, the effect of lowering the power consumption by reducing the brightness of the light irradiated by the backlight unit 3 is more reliably exhibited than before, and a black screen is lit with high brightness. It is possible to suppress the occurrence of black floating caused by this and the accompanying deterioration in image quality.

  Further, the luminance adjusting unit 53 sets the adjustment value of the luminance of light emitted from the subunit 3A constituting the unit display system between the luminance indicating white display and the luminance indicating black display. Is preferably allocated according to the histogram created. When the entire pixel block 1A is in white display, it is the brightest of all display patterns. Therefore, the luminance indicating this white display is set as the highest luminance among the adjustment values of the luminance of light emitted by the subunit 3A. Set. On the other hand, when the entire pixel block 1A is in black display, it is the darkest of all display patterns. Therefore, the luminance indicating this black display is the smallest of the adjustment values of the luminance of the light emitted by the subunit 3A. Set as brightness. As a result, it is possible to easily estimate and adjust the maximum and minimum luminances, and to suppress the occurrence of inversion of light and dark in an image including white display and / or black display. Video can be realized.

  Further, according to the above configuration, for each gray level luminance I1 to Ix, each addition operation value K1 to Kx that is larger than the corresponding maximum value M1 to Mx is replaced with the corresponding maximum value M1 to Mx. . When each of the addition calculation values K1 to Kx becomes too large, the adjustment value of the luminance of the light emitted from the subunit 3A constituting the unit display system becomes a very large value, which results in high power consumption. However, by setting the maximum values M1 to Mx for the respective addition calculation values K1 to Kx, the adjustment value becomes very large, and the power consumption increases accordingly. Can be suppressed.

  Further, the unit adjustment values F (I1) to F (Ix), which are adjustment values of the luminance of light to be given to one pixel for which the gray level luminances I1 to Ix are calculated, and the addition calculation values K1 to K1. The predetermined maximum values M1 to Mx corresponding to Kx are preferably a function that monotonically increases with respect to the increase from the gray level luminance I1 to the gray level luminance In, and more preferably a function that is proportional. Is preferred.

  Accordingly, corresponding to the brightness of the image displayed on the pixel block 1A constituting the unit display system, the pixel block 1A is bright in the pixel block 1A portion where the image is bright and the pixel block 1A portion where the image is dark. This is convenient because the correspondence that the pixel block 1A is lit darkly can be given more clearly.

  By the way, if each unit adjustment value F (I1) to F (Ix) is a small value, for example, when noise is superimposed on the video signal, there is only one white point on the whole black screen. Sometimes, the brightness of the light emitted from the subunit 3A remains dark, so that it is possible to obtain an easy-to-view image with little black floating. However, if the unit adjustment values F (I1) to F (Ix) are too small, the starry sky and subtitle characters, etc., which are displayed brightly with a relatively small number of pixels will be displayed darkly. In actuality, it is preferable that the size is about 1/80 to 1/50 of the corresponding maximum values M1 to Mx. That is, the maximum value My is preferably set to a value that is about 50 to 80 times the corresponding unit adjustment value F (Iy).

  Meanwhile, a unit display system (hereinafter referred to as “proximity unit display system”) adjacent to the target unit display system is included in the pixel block 1A constituting a certain unit display system (hereinafter referred to as “target unit display system”). ) Is further irradiated by diffusion. Here, for example, when the adjustment value of light emitted from the subunit 3A constituting the proximity unit display system is large (that is, the subunit 3A constituting the proximity unit display system shines brightly), the proximity unit is displayed. The light emitted from the subunit 3A constituting the display system is further emitted to the pixel block 1A constituting the target unit display system. For this reason, even if the adjustment value of the light irradiated by the subunit 3A constituting the target unit display system is reduced, the brightness of the pixel block 1A constituting the desired target unit display system can be obtained.

  Therefore, the gray level luminance extraction unit 51, the histogram creation unit 52, and the luminance adjustment unit 53 perform the above-described series of processing on the plurality of pixel blocks 1A and the subunit 3A corresponding to each pixel block 1A. It is preferable that the luminance of light emitted from the subunit 3A constituting the target unit display system is adjusted twice or more according to the luminance of light emitted from the subunit 3A constituting the proximity unit display system. . In this way, the value of the pixel block 1A is calculated again according to the value of the adjacent pixel block 1A, and is set as a new adjustment value of the light irradiated by the corresponding subunit 3A, thereby further reducing the power consumption. It becomes possible.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The present invention can more reliably obtain the effect of reducing power consumption in a display device including a liquid crystal display panel as a display unit and a backlight unit corresponding to the liquid crystal display panel. It has the effect of being able to achieve high image quality. Therefore, the present invention can be applied to various liquid crystal display devices.

It is a figure which shows schematic structure of the display apparatus which concerns on one embodiment of this invention. It is a histogram which shows the example of a histogram preparation in the histogram preparation part of the said display apparatus. It is a graph explaining an example of the calculation point for calculating | requiring the adjustment value of the light irradiated to the pixel block which a subunit respond | corresponds from the said histogram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 1A Pixel block 3 Backlight unit 3A Subunit 4 Light emitting diode 5 Display gradation analyzer 51 Gray level luminance extraction part (gray level luminance calculation part)
52 Histogram creation part (pixel integration part)
53 Brightness adjustment unit 100 Liquid crystal display devices F (I1) to F (Ix) Unit adjustment values I1 to Ix Gray level luminances K1 to Kx Addition calculation values M1 to Mx Maximum values N1 to Nx Number of pixels

Claims (11)

The display area includes a liquid crystal display panel divided into a plurality of pixel blocks, and a backlight unit divided into a plurality of subunits for irradiating light for each of the plurality of pixel blocks. , A display device capable of independently adjusting the brightness of light applied to each corresponding pixel block,
With respect to at least one selected pixel block, the gray level luminance of the image displayed on each pixel constituting the pixel block, obtained from the data of the image to be displayed in the display area of the liquid crystal display panel, is calculated. A gray level luminance calculator;
A pixel integration unit that integrates the number of pixels for which the gray level luminance is calculated for each gray level luminance calculated by the gray level luminance calculation unit;
A display device, comprising: a luminance adjustment unit that adjusts the luminance of light emitted from each subunit corresponding to the selected pixel block according to a result of integration by the pixel integration unit. The brightness adjustment unit
The adjustment value of the luminance of light emitted by each of the subunits is allocated according to the result of the integration by the pixel integration unit between the luminance indicating white display and the luminance indicating black display. The display device according to claim 1. The brightness adjustment unit
For each gray level luminance calculated by the gray level luminance calculation unit, a unit adjustment value of light luminance to be given to one pixel for which the gray level luminance is calculated, and the number of pixels for which the gray level luminance is calculated A first operation for obtaining a product of
The brightness adjustment value of the light emitted by each of the subunits is determined by performing a second calculation of adding all the products obtained by the first calculation. Item 3. The display device according to Item 1 or 2. In the second calculation, the products obtained by the first calculation are added in order from the smallest gray level luminance,
When the addition operation value obtained by adding one product is larger than a predetermined maximum value corresponding to the addition operation value, the addition operation value is replaced with the corresponding maximum value. The display device according to claim 3.   The display device according to claim 4, wherein each of the corresponding maximum values is determined so as to monotonically increase with respect to an increase in the gray level luminance related to each of the addition calculation values.   6. The display device according to claim 4, wherein each of the corresponding maximum values is proportional to the increase of the gray level luminance related to each of the addition calculation values.   7. The display device according to claim 3, wherein each of the unit adjustment values is determined so as to monotonically increase with respect to the increase in the gray level luminance.   The display device according to claim 3, wherein each of the unit adjustment values is determined so as to be proportional to an increase in the gray level luminance. The gray level luminance calculation unit, the pixel integration unit, and the luminance adjustment unit,
Each of the above processes is performed on a plurality of the pixel blocks and the subunits corresponding to the pixel blocks.
The brightness of light emitted by other subunits adjacent to the subunit is adjusted twice or more according to the brightness of light emitted by the subunit corresponding to the selected at least one pixel block. The display device according to claim 1.   The display device according to claim 1, wherein the backlight unit includes a light emitting diode as a light source for irradiating light. The display area includes a liquid crystal display panel divided into a plurality of pixel blocks, and a backlight unit divided into a plurality of subunits for irradiating light for each of the plurality of pixel blocks. , A display control method capable of independently adjusting the brightness of light applied to each corresponding pixel block,
With respect to at least one selected pixel block, the gray level luminance of the image displayed on each pixel constituting the pixel block, obtained from the data of the image to be displayed in the display area of the liquid crystal display panel, is calculated. A gray level luminance calculation step;
A pixel integration step of integrating the number of pixels for which the gray level luminance is calculated for each gray level luminance calculated in the gray level luminance calculation step;
A display control method comprising: a luminance adjustment step of adjusting the luminance of light emitted from each subunit corresponding to the selected pixel block in accordance with a result of the integration of the pixel integration step.

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